1. Field of the Invention
The present invention relates to a machine element of the type having at least a fitting member pressure-fitted on a shaft, such as a camshaft for use in internal combustion engines, a shaft-supported gear, and a shaft-supported rotor. The fitting member has a bore for receiving the shaft, which is eccentric to the center of the fitting member for use in the camshaft or the like and concentric in the shaft-supported gear or the like. At least one portion of the area of the shaft in which the fitting member is to be provided has a diameter which is greater than the remaining areas of the shaft. The bore has at least a narrow portion defining a spacing diametrically smaller than the increased diameter portion of the shaft. The fitting member is forced onto the increased diameter portion of the shaft with the narrow portion of the bore cutting and/or deforming the increased diameter portion.
The present invention a also relates to a method of manufacturing the above-described machine element.
2. Description of the Prior Art
Machine elements are known in which the fitting members and the shafts, separately manufactured, are assembled by a press fit accompanying a chip-removing operation. U.S. Pat. No. 4,903,543 or U.S. Pat. No. 4,947,547 describes a camshaft which includes a shaft and at least one cam slid onto and connected to the shaft in an area of the shaft. The cam defines a bore for receiving the shaft. The bore has at least one radially inwardly directed projection. At least one portion of the area off the shaft has a diameter larger than the remaining areas of the shaft. The increased diameter portion of the shaft is a bead-like material displacement which extends circumferentially on the shaft and is manufactured by rolling. The cam is forced onto the increased diameter portion of the shaft with a projection in the bore of the cam for forming in a chip-removing operation, a groove in the increased diameter portion.
The projection is so finished as a cutting edge with an angular cross-section to form the groove in the outer surface off the shaft. It is also required for the fitting member to be harder than the shaft, since the fitting member must cut the groove off on the shaft with its projection. However, it is not easy to provide and finish the axially extending angular projection as a cutting edge within the bore of the fitting member. The cost of manufacturing the camshaft considerably rises when the fitting member is made from a harder material for coupling with the relatively hard shaft.
The object of the present invention is to provide a machine element in which at least one fitting member is pressure-fitted onto the increased diameter portion of a shaft with at least an inner wall portion of the fitting member shaving and/or deforming the outer surface of the shaft for a tight connection therebetween, while the fitting member is manufactured with ease at a relatively low cost. Another object of the present invention is to provide an assembling method to manufacture the aforementioned machine element.